Deterministic and low-latency communications for multi-application mesh networks in the sub-GHz band

The rapid expansion of the Low-power and Lossy Networks (LLNs) has revolutionized connectivity, driving the development of networks tailored for low-power, lossy environments. These networks support diverse applications, including smart cities, smart utilities, and industrial automation, where energy efficiency, low and bounded latency, and end-to-end network reliability are critical. Wireless Smart Ubiquitous Network (Wi-SUN) is one of the leading communication standards for such environments. It is based on a collection of open standards and differentiates itself from the other Internet of Things (IoT)-based technologies by being natively IPv6-based, meshed, and using sub-GHz bands.

Wi-SUN relies on the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) routing protocol. This protocol organizes network nodes into a hierarchical structure using a Destination-Oriented Directed Acyclic Graph (DODAG). It enables efficient multipoint-to-point communications (from devices inside the LLN towards the DODAG root node) and point-to-multipoint communications (from the DODAG root node to a subset of devices inside the LLN). However, the increasing demand for point-to-point (peer-to-peer) communications between devices inside the LLN highlights inherent limitations in the standard RPL design.

RPL is ideal for communications between the nodes of a Field Area Network (FAN) and a central node (DODAG root) or towards the Internet. While many applications follow such a traffic pattern, others need mainly peer-to-peer communications.  For instance, smart streetlights need to send a message to their neighbors to turn on (or to increase their brightness) whenever they detect a pedestrian or a vehicle.  There is no need for such messages to reach the root; doing so would only increase the latency and the network traffic. The most efficient and fastest solution is for streetlights to exchange messages directly, as they are typically close enough to each other to communicate directly.

The dissertation aims to propose and implement new mechanisms to guarantee Quality of Service (QoS) in Wi-SUN networks, namely low latency, low jitter, and reliable message delivery. While several proposals for peer-to-peer communications in RPL networks exist, they do not offer any QoS guarantees. The work of the Reliable and Available Wireless (RAW) working group of the Internet Engineering Task Force could be a starting point.

After proposing one or more solutions, the Ph.D. candidate will evaluate their performance through simulations and will implement at least one solution in the Silicon Labs stack.